Abstract
Steam-based huff-and-puff technology has gained a great deal of attention in heavy oil thermal recovery, which however suffered water invasion and steam channeling. In addition, the high-temperature and -salinity seriously restrict the implementation of conventional blocking agents. Here, an innovative composite foamed gel formula consisting of a novel toughening agent is developed to adapt such harsh conditions (175 degrees C, 20 x 104 mg/L). Specifically, orthogonal testing is carried out for formula evaluation and optimization, during which the influences of component concentration, temperature, pH and salinity on the gelling time and gel strength are determined experimentally. The formation and toughening mechanism are illustrated by infrared spectroscopy and scanning electron microscopy (SEM). Blocking performances of ordinary foam, gel and novel foamed gel are compared through sandpack floodings. It is shown that the optimal formula is composed of 4.3 wt% alkali lignin, 0.35 wt% toughening agent, 4 wt% phenolic resin and 0.5 wt% foaming agent. The gel strength reaches G level at 160 degrees C after 3.5 h. The gel is still stable at 175 degrees C under a dehydration rate of 10% after one month. Even under 20 x 104 mg/L salinity, the gel strength still reaches the G level after 22 h. Much higher resistance factor of the alkali lignin foamed gel have been achieved over ordinary foam and gel. The innovative foamed gel here could adapt the harsh conditions perfectly to mitigate the adverse impacts of water invasion and steam channeling, which in turn improves the steam-based puff-and-huff efficiency significantly.
NSTL
Elsevier